The invention relates to an electrodeless low-pressure discharge lamp having a lamp vessel which is sealed in a gas-tight manner and which is filled with a metal vapor and a rare gas, and has a core of a magnetic material. During operation of the lamp, an electric field is generated in the lamp vessel by means of a winding surrounding the core and a high-frequency supply unit connected thereto. A transparent electrically conducting layer is present on the inside of the lamp vessel which is connected to an electric conductor located outside the lamp vessel by means of a lead-through member incorporated in the wall of the lamp vessel. A lamp of this type is known from Japanese Kokai No. 53-4382 (Application No. 51-78660).
In the known lamp the inside of the lamp vessel has a transparent conducting layer in order to prevent high-frequency electric interference currents from being produced in the mains. The conducting layer is connected to a rod-shaped lead-through member which is incorporated in the wall of the lamp vessel. It has been found that it is advantageous to connect the said conducting layer to one of the supply wires of the mains so as to reduce the said interference currents as described in U.S. Pat. No. 4,568,859.
To comply with the standards imposed with respect to the maximum admissible value of the interference, the said conducting layer should be relatively thick. This is a drawback, because it has a negative influence on the light output of the lamp. Moreover, it is troublesome and costly to provide such a comparatively thick layer.